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Re: not-a-number's
On 2013-01-17 06:53:45 +0100, Mischa Baars wrote:
> Also this was not what I intended to do, I was trying to work with quiet
> not-a-numbers explicitly to avoid the 'invalid operation' exception to be
> triggered, so that my program can work it's way through the calculations
> without being terminated by the intervention of a signal handler. When any
> not-a-number shows up in results after execution, then you know something
> went wrong. When the program does what it is supposed to do, you could
> remove any remaining debug code, such as the boundary check in the
> trigonometric functions.
Checking whether a (final) result is NaN is not always the correct way
to detect whether something was wrong, because a NaN can disappear.
For instance, pow(NaN,0) gives 0, not NaN. You need to check the
"invalid operation" exception flag (if you don't want a trap). And
this flag will also be set by the <=, <, >, >= comparisons when one
of the operands is NaN, which should be fine for you.
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